Updated

A Denver man believed to be the only consumer to develop "popcorn lung" from regular servings of microwave popcorn filed a lawsuit Tuesday claiming injury from the artificial butter flavoring that previosly sickened only popcorn factory workers.

Wayne Watson's attorney, Kenneth McClain, said the suit names the Kroger Company and two of its divisions: grocery store King Soopers' parent company, Dillon Companies Inc., and food distributor Inter-American Products Inc.

The case was filed Tuesday in U.S. District Court. A spokeswoman for Kroger said the company does not comment on lawsuits.

Watson's case of "popcorn lung" and his two-bags-a-day diet made national news last year when doctors at National Jewish Hospital diagnosed him with the rare lung condition that has been linked to the flavor chemical diacetyl.

The chemical was the subject of lawsuits and multi-million-dollar verdicts in 2004 and 2005 from factory workers testing and inhaling the fumes from hundreds of bags of microwave popcorn a day. Ten workers at the Gilster Mary Lee factory in Jasper, Mo. were placed on lung transplant lists.

Watson is represented by the same firm that filed suit in Missouri — Humphrey, Farrington & McClain of Independence, Mo.

"This is new, but not surprising," attorney Kenneth McClain said in a statement. " Workers at the Jasper plant whose only job was to pop microwave popcorn in the quality control department got sick, so it's not surprising that someone like Mr. Watson could be at risk."

Diacetyl is a naturally occurring chemical compound that gives butter its flavor. It is also found in cheese and some wines, according to the National Institute of Occupational Safety and health. It has been approved by the Food and Drug Administration as a flavor ingredient.

After the workers became ill, new workplace standards were developed that isolated microwaves from workers testing popcorn bags coming off the manufacturing line.

Last month, the nation's four biggest makers of microwave popcorn announced they were reformulating their recipes to remove the chemical from nearly all their products. It might take several months for the reformulated popcorn to replace all the older varieties on store shelves.

Dr. Cecile Rose, a lung specialist at National Jewish, diagnosed Watson with the rare disease officially called bronchiolitis obliterans. She told the Associated Press in September that there was no certan link between Watson's copious popcorn servings and the disease, but she said "the possibility raises concern."

An investigation by the hospital found levels similar to factory workers were exposed to between .75 to 4 parts per million of diacetyl. Tests in Watson's kitchen where the microwave would vent and where he would open popcorn bags were between .5 and 3 parts per million, according to the hospital.